Process of cutting contact points



April 22, 1941. DE GRAEVE 2,239,456

PROCESS OF CUTTING CONTACT POINTS Filed Aug. 29, 1938 INVENTOR. 7315700055 DEEEEEVE BY WM r I ATTO EY.

Patented Apr. 22, 1941 PROCESS OF CUTTING CONTACT POINTS Theodore DeGraeve, Detroit, Mich.

Application August 29, 1938, Serial No. 227,313

3 Claims.

My invention relates to a new and useful improvementin the process ofcutting contact points for use on penetrators and the product resultingfrom the process. The class of penetrators referred to consists of ahard point generally formed from a diamond and mounted in a holder soarranged and constructed that the penetrator may be pressed against thesurface of a material which it is desired to test for hardness. Thedegree of penetration into the material tested under a pre-. determinedpressure indicates the hardness of the material tested.

In the mounting of diamonds in holders, an objectionable featureis thatwhen the penetrator is subjected to pressure the diamond is frequentlyforced into the holder andit is an object of .the present invention toprovide a penetrator diamond so constructed and arranged as to preventthe penetnation of the same into the holder.

Another object of the invention is the provision of a penetrator diamondso constructed and arranged as to be possessed of maximum effiof apenetrator diamond so formed and mounted as .to prevent oscillation ortilting when brought into contact with the material to be tested.

Other objects of the invention will appear hereafter.

The invention consists in the combination and In the drawing I haveillustrated an octahedron diamond and each of the faces of the diamondis provided with sections I, 2, 3 and 4. While I have illustrated theoperation of the invention on a diamond, I do not necessarily limitmyself .to the formation of a penetrator contact member from diamonds,as other materials may lend themselves to this purpose with satisfactoryresults and with which materials the present invention may be employedequally as well as with diamonds or nearly so.

It will be noted that the grain 5 of the section 3 extends at rightangles to the grain 5 of the section 4 and the apex 6 of the section 3is used to locate approximately the contact part of the sphericalsurface I of the finished body. The penetrator point is cast in theholder II, so that the holder, after the casting operation, is providedwith a socket III in which the penetrator point is engaged. The firststep in the operation is the removal of one of the apices or heelsof theoctahedron to provide the flat surface 9 so that when the point is castin the holder II, the flat surface 9 will bear against the flat surfaceIII of the holder II. Thus there is a large area of the penetrator whichserves to deliver the thrust to the holder II and in this manner forcingof the penetrator point into the holder itself is arrangement of partshereinafter described and claimed.

The invention will be best understood by reference to the accompanyingdrawing which forms a part of this specification, and in which Fig. 1 isa side elevational view of a diamond of the octahedron design.

Fig. 2 is a side elevational view of the diamond showing one step in theprocess of formation.

Fig. 3 is a side elevational view illustrating a further step in themanufacture.

Fi 4 is a side elevational view of a diamond point showing the completedportion.

Fig. 5 is a section-a1 view of the diamond point mounted in a holderpreparatory to formation.

avoided. This forcing of the penetrator point into the holder iscommonly referred to as sinking or drifting and is a 'difiiculty whichis commonly encountered. As shown in Fig. 5 when the penetrator point iscast in the holder I I, the apices l2 and I3 serve as anchorages forsecurely anchoring the contact member or penetrator in the holder I I.

The penetrator when finished is provided with an outwardly projecting orexposed portion having a spherical surface and constitutingsubstantially a semi-sphere projecting outwardly from the end of theholder I I. The penetrator shown in Fig. 2 is operated upon "after ithas been cast in the holder and by such operation the exposed portion isreduced to the contour shown in Fig. 4. This contour is a sphericalcontour and it is centered on the longitudinal axis of the holder II. Itis brought into spherical formation by means of a cutting operation inwhich the body is cut inwardly into various steps 8 to provide theformation shown in Fig. -3. After this cutting into stepped formation iscompleted, the penetrator is then subjected to a grinding operation toproduce the spherical surface 1 shown in Fig. 4. This surface I will, ofcourse, be a smooth have been removed.

In cutting the penetrator into the stepped formation shown in Fig. 3,these various steps result in a plurality of faces or facets and each ofthese facets is out according to the grain of the section in which itappears so that a fracturing or splitting of the facet is avoided. Itwill also be noted from Fig. that when the penetrator is completed andstrain is exerted upon the center point, the strain will be directedangularly to the length of the grain and thus a tendency to flex ispresent and a fracturing strain thus avoided.

In the use of diamond contact members .or penetrators, a commonconstruction provides an initial contact point with a spherical engagingsurface which proceeds from the spherical formation into a conicalformation, proceeding inwardly from the outer end of the diamond. In

the use of such penetrator diamonds, great difiiculty is encountered inproper centering. The initialcontact is efiected on a spherical surfaceandthen as the pressure is exerted, the pressure is transmitted from thespherical surface onto a conical surface. Unless this spherical surfaceis centered with the conical surface accuracy cannot be obtained. Withthe penetrator diamond constructed in accordance with the presentinvention, this difliculty of centering resulting from the use of twoformations is entirely avoided. Moreover, when the initial contact withmy invention is effected, it is effected on a center which does notchange as subsequent pressure is exerted. This results in a higherdegree of accuracy and prevents the tendency to tilt which ordinarilyresults from a shifting of centers or lines of pressure.

With a penetrator diamond constructed in this manner, I have madepossible the construction of a penetrator which will be accurate, inwhich tilting will be avoided, and in which the sinking of thepenetrator into the holder is prevented. In the process of manufacturean economical operation is provided and one which facilitates theformation of a true spherical peripheral surface so that a multiplicityof contact points is. thus presented.

While I have illustrated and described the preferred form ofconstruction, I do not wish to limit myself to the precise details ofstructure shown, but desire to avail myself of such variations andmodifications as may come within the scope of the appended claims.

What I claim as new is:

1. The method of forming a contact point from an octahedron diamondconsisting in removing a portion of said diamond to form a backingsurface and cutting said diamond from opposite apices in a steppedformation to approximate the shape desired and removing the steps toprovide an uninterrupted smooth curvilinear peripheral surface.

2. The method of forming a contact point from an octahedron diamondconsisting in cutting said diamond in stepped formation from adjacentopposite apices toward an intermediate apex to approximate the shapedesired and removing said steps in a grinding operation to provide asmooth uninterrupted curvilinear peripheral surface.

3. The method of forming a contact point from an octahedron diamond conssting in removing one of the apieces of said diamond and cutting saiddiamond from adjacent a pair of opposite apices proceeding toward anintermediate apex in stepped formation and grinding off said steps toprovide a smooth uninterrupted substantially spherical peripheralsurface.

THEODORE DE GRAEVE.

